1. Field of the Invention
This invention relates to a method and apparatus for automatically and successively cutting off the top seal parts of containers made of synthetic resin traveling continuously along a production line.
2. Description of the Prior Art
Containers made of flexible synthetic resin, particularly blow-molded containers, ordinarily have top seal parts formed integrally with their opening or top parts. For this reason, it is necessary to cut off and remove these top seal parts in a process stage prior to charging the content product into the containers.
Heretofore, the principal means for cutting off the top seal parts of such containers have been: (A) that wherein, as each container is caused to rotate, a cutting blade is caused to move in a direction perpendicular to the axial direction of the container against the part to be cut off the top seal part thereby to cut off the same (as disclosed, for example, in Japanese Patent Publication Nos. 3350/1970 and 23584/1973); (B) that wherein each container is fixed, and its top seal part is sheared off by a pair of cutting blades (as disclosed, for example, in Japanese Patent Publication No. 6875/1969); and (C) that wherein each container is placed in a horizontal state, and, as it is being conveyed, its seal part is cut off by a fixed cutting blade (as disclosed, for example, in Japanese Patent Laid-Open No. 79112/1980).
However, in means wherein the cutting is performed as rotation is imparted to the container as in (A) above, it is necessary to so construct each of the support devices for supporting individual containers that they can rotate and, moreover, to provide a driving device for driving them in rotation. For this reason, the entire apparatus becomes very complicated, and, at the same time, unless rotation is imparted to each container as it is held in an upright state, the cut plane will not be flat. More particularly unless the container has a shape which is symmetrical around its centerline and, moreover, has a specific hardness or rigidity, the application of this means is difficult. Consequently, the containers to which this means can be applied is greatly restricted.
In means wherein the top seal part of the container is sheared off by a clamping action of a pair of shearing blades as in (B) above, or in means wherein cutting is accomplished by pressing the part of the container to be cut against a fixed knife as in (C) above, a force for pressing the cutter against the opening or top part of the container is additionally applied. For this reason, in the case of a circular top part, it is cut in a deformed elliptical shape by a force in a direction perpendicular to the cutter. Consequently, the cut edge tends to be deformed, whereby the screw threads around the top part of the container are apt to be damaged. In the case where the container is made of a flexible material, the cut edge is not flat, and the sealing effect when a cap is screwed onto the container top will be poor.
Furthermore, in an apparatus wherein cutting is carried out with each container placed in a horizontal state, it is necessary to feed the containers in upright state, thereafter to place them in horizontal state, to hold them in that state to carry out cutting, to place the containers once again in upright state, and to move the same to the succeeding process. For this reason, the entire apparatus unavoidably becomes large, and its mechanisms become complicated.